1. Field Of The Invention
The present invention relates to cellular foams characterized by carbodiimide, isocyanurate and urethane linkages. More particularly, the invention relates to foams prepared by catalytically condensing an organic polyisocyanate in the presence of certain catalysts and combinations of polyoxyethylated polyols.
2. Prior Art
The preparation of foams characterized by carbodiimide, isocyanurate and urethane linkages by catalytically condensing an organic polyisocyanate in the presence of a primary hydroxy-terminated polyol is described in U.S. Pat. No. 3,922,238. The resulting foams exhibit acceptable strength properties and flame retardancy at lower levels of polyol use. While the strength properties of these foams may be further improved by increasing the ratio of polyol to isocyanate, this in turn causes a reduction in flame retardancy. The present invention is directed to an improvement in the process and compositions described in U.S. Pat. No. 3,922,238.